Extract the code for supporing extended desktop from WorkspaceWindowResizer into DragWindowResizer.

ash/wm/window_resizer.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_WM_WINDOW_RESIZER_H_
 #define ASH_WM_WINDOW_RESIZER_H_
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 106 matching lines @@
                              int* delta_x);
 
   // Returns the height of the drag.
   static int GetHeightForDrag(const Details& details,
                               int min_height,
                               int* delta_y);
 };
 
 // Creates a WindowResizer for |window|. This can return a scoped_ptr
 // initialized with NULL if |window| should not be resized nor dragged.
-scoped_ptr<WindowResizer> CreateWindowResizer(
+ASH_EXPORT scoped_ptr<WindowResizer> CreateWindowResizer(
     aura::Window* window,
     const gfx::Point& point_in_parent,
     int window_component);
 
 }  // namespace aura
 
 #endif  // ASH_WM_WINDOW_RESIZER_H_